In a wireless network, a wireless access point connects wireless communication devices together to form the wireless network. The access point usually connects to a wired network, and can relay data between wireless devices and wired devices. Several access points can link together to form a larger network that allows a user of a wireless device to roam between access points without the connection being dropped.
802.11 is an IEEE (Institute of Electrical and Electronics Engineers) standard for wireless area networks. 802.11 wireless devices typically have a mode for transmitting and receiving data traffic, and a mode for scanning for available access points during a process called background scanning. Up until 2004, 802.11 wireless devices had a single antenna (some devices had two antennas, but there was only one set of components to process the signal, or RF chain).
Because a 802.11 wireless device has a single antenna, in order to perform a background scan, the device has to stop transferring data over a data channel, switch to a scan channel, and then perform the background scan by transferring scan data over the scan channel for short periods time (e.g., a couple of milliseconds) to detect available access points. After the background scan is completed, the device has to switch back to the data channel, and restart the transmitter to transfer data traffic. The stopping and starting of data traffic to perform a background scan negatively influences the data throughput of the wireless device, since the wireless device is not able to send or receive during this scanning period.
802.11 task group N (TGn) has recently proposed an 802.11n standard that has the goal of increasing the peak data throughput transmitted by a wireless multiple-input/multiple-output (MIMO) device to 100 Mbps. The basis of MIMO operation is to provide 11n devices with multiple radio interfaces to allow the devices to send data on different channels at the same time in order to achieve greater transmit/receive data rates than the pre-11n devices. In its present form, the 802.11n standard is silent as to how background scanning should be implemented. Using the traditional background scan process in which all data traffic is temporarily suspended would be counterproductive to the goal of the proposed 802.11n standard of increasing throughput. Accordingly, it would be desirable to provide an improved background scan process for use in multi-radio equipped wireless devices.